S.N.A.K.E.: A Dynamically Reconfigurable Artificial Sensate Skin ...

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Figure 5-2: Skin Patch bending profile the strain gages are only minimally stimulated. For this reason, data plots shown for strain gages are not shown for the entire Skin Patch, but rather for individual nodes so that the reader can have an idea of their actual performance. 5.1.3 Pressure Sensors The third mechanical characteristic that had a deep effect on the sensing behavior of the nodes is related to the pressure sensors. Pressure sensors use a special material that has to be bonded to electrodes placed on the surface of the nodes. However since the electrodes must be in direct touch with the sensing material, no glue can be placed in the active sensor area. Moreover, Skin Nodes had to be very small to maintain a good sensing density, which left very little space that could be used to glue the material to the substrate. To bond the QTC material to the substrate, a 3M 77 Super Spray Adhesive was used. This glue was applied to the nodes with a mask, so that the sensor electrodes were not coated. However, this glue is semi-liquid when first applied, and because the area available for bonding was so reduced, even if the sensor electrodes were masked, some of the glue was spilled on them making some sensors more sensitive than others and some not sensitive at all. A way better way of bonding the QTC material to the nodes would have been to use adhesive tape instead of glue, which is easier to correct, cleaner and easier to handle. This lesson was learned later in the assembly process though, and therefore some of the sensors 108
of the assembled skin patch don’t work as well as they should. So when these are analyzed, only data plots of the sensors that were not affected will be shown. Finally, it is important to remark that even though pressure sensors and strain gages were affected by these mechanical flaws, they were actually more sensitive than actually expected, when they were first tested before the entire patch was assembled. Other sensing modalities that did not depend on the mechanical characteristics of the system design were obviously not affected by these problems, so the entire Skin Patch could be easily scanned by the PC sampling application as it was originally intended. 5.2 Sensor Data and Sensing Ranges Several experiments were carried out to test the functionality of the designed platform. Two patches of skin (one with 12 nodes and another one of 4) and two Brains were fabricated and assembled to test both modes of operation of the Skin Patches: stand-alone mode, and data-extraction mode. This section is divided into two subsections: the first one will show how each one of the sensing modalities performed along with data plots extracted for each one of them using a skin patch as a data extraction device; the second one will demonstrate the functionality of the same patch used in stand-alone mode. 5.2.1 Skin Patches as Data-extraction Devices To analyze how well each one of the sensing modalities performed, they were first calibrated if necessary and then data was extracted from them. Since each one of the sensing modalities was analyzed separate from each other, results will be presented according to the sensing modality they were obtained from. Although only one data set was extracted for each sensing modality, the extracted information will be shown in two different ways: the first will show some snapshots taken from the real-time 3D OpenGL control from the GUI application when the sampling process started to illustrate its functionality; the second set corresponds to plots created with the data saved by the application at the moment of 109
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Author S.N.A.K.E.: A Dynamically Re
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S.N.A.K.E.: A Dynamically Reconfigu
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Table of Contents Abstract 3 Acknow
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List of Figures 2-1 Created by MIT
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E-1 OpenGL Control Header File . .
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Chapter 1 Introduction “Imaginati
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The current project, named S.N.A.K.
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Hardware Each Skin Patch is compose
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living tissue. Particularly in the
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Figure 2-2: Leonardo’s Hand great
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Artificial Sensate Skins elsewhere
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2.1.2 Ultra-dense Sensor Arrays Thi
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2.2 Flexible Circuits Although, not
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2.2.2 Other Technologies Figure 2-6
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human skin. The following design pr
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(a) Skin Patches as data extraction
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Figure 3-3: I 2 C Routing pattern T
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3.2.2 Peer to Peer As we already me
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5. Audio: by adding a MEMS micropho
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Table 3.1: Material thicknesses and
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(a) Node Front (b) Node Back Figure
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Figure 3-9: Skin Patch mechanical t
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used, which only further complicate
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8. Teardrops and filleting were add
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(a) 7.4V, 2.2mAh Li-ion Battery (b)
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Page 60 and 61: has a 30mA forward current with a f
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Page 66 and 67: Figure 3-16: QTC response curve for
Page 68 and 69: (a) Prototype boards used to calibr
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Page 72 and 73: Sound The only sensing modality add
Page 74 and 75: Figure 3-20: Brain regular PCB fabr
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Page 81 and 82: Networks. Why is this relevant? Mai
Page 83 and 84: Figure 4-1: Bootloader memory map C
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Page 87 and 88: Figure 4-3: Sampling timing example
Page 89 and 90: We also mentioned before that there
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Page 93 and 94: Component Description 1 Indicates t
Page 95 and 96: last chapter. Figure 4-5: Automatic
Page 97 and 98: An important point to stress is tha
Page 99 and 100: (a) Rotation control (b) Zooming co
Page 101 and 102: 4.3 Communications Software The las
Page 103 and 104: 4.3.2 Peer to Peer Peer to peer com
Page 105 and 106: Chapter 5 Analysis of Results and E
Page 107: Figure 5-1: Stress concentration po
Page 111 and 112: Node SG1 SG2 R(X) R(Y) Δ(X) Δ(Y)
Page 113 and 114: Or, ∆R = R3 R3 R3 + RC (5.2) Howe
Page 115 and 116: R3 Microstrain 162Ω −99.7337969
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Page 125 and 126: Data plots were also extracted for
Page 127 and 128: (a) Temperature sensor data plots (
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Page 133 and 134: 5.3 Performance Metrics We have pre
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Page 139 and 140: Finally, since power is readily ava
Page 141 and 142: Chapter 6 Conclusions and Future Wo
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Page 147 and 148: Appendix A Abbreviations and Symbol
Page 149 and 150: Appendix B Bill of Materials 149
Page 151 and 152: Appendix C Schematics and PCB Layou
Page 153 and 154: 1 1 2 2 3 3 4 4 D D C C B B A A Tit
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Cain P0C ain01 P0Cain02 L1 P0L101 P
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Figure C-10: Node Bottom Overlay 16
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4 3 2 1 A A Brain Communications Ac
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C3v P0C3v01 P0C3v02 Cavcc P0Cavcc01
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Appendix D Firmware 167
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C:\Documents and Settings\Gerardo\M
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Appendix E PC Code 183
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1 c:\Documents and Settings\Gerardo
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12 c:\Documents and Settings\Gerard
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Bibliography [1] John C. Ansel. Ski
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[33] Joseph Jacobson, B Comiskey, C
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[68] Vilis Tutis. The physiology of
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